The present invention relates to a peristaltic pump for fluid transfer, such as blood circulation, dialytic fluid circulation or fluid medicine injection, and more particularly, to an adjustable occlusion peristaltic pump having an automatically adjusting bushing.
Peristaltic pumps are commonly utilized in medical applications. For instance, such pumps are often employed during cardiovascular surgery to facilitate circulation of blood between a patient and a heart-lung machine. Other common medical uses are the transfer of blood between a patient and a kidney dialyzer, and intravenous feeding of IV solutions. Generally, peristaltic pumps are simply structured, generate a constant flow, and employ disposable tubes as a member for fluid transfer.
Peristaltic pumps are relatively simple in construction and typically include a housing having rollers which progressively compress a flexible tube at spaced intervals against an arcuate surface or raceway so as to flatten or locally reduce the cross-sectional area of the tube. In this manner, fluid leading to the flexible tube is continuously forced through the flexible tube by one or another of the rollers as it proceeds along the flexible tube over the arcuate surface or raceway.
A conventional roller pump 10, as shown in FIG. 1, comprises a drive mechanism 14 furnished with a drive shaft 12, a rotating shaft 16 which rotates according to the rotation of drive shaft 12, and a hollow pump head 20 fixed to a housing 18 to which drive mechanism 14 is attached. This pump head 20 integrally incorporates a bearing block 24 through which rotating shaft 16 is inserted and rotatably supported by a pair of bearings 22 and a stator 26 arranged on the upper portion of bearing block 24. On the upper surface of stator 26 is formed a recess 28 through which the upper end of rotating shaft 16 is protruded. While this recess 28 is radially and outwardly spaced at a certain distance from the outer circumferential surface of rotating shaft 16, its inner circumferential surface 28a is coaxial with rotating shaft 16.
A rotor assembly 30 is attached to the upper portion of rotating shaft 16 in such a way as to be placed inside recess 28 of stator 26 and to stay opposite the inner circumferential surface 28a thereof. This rotor 30 is fixed to rotating shaft 16 through a bolt 32, and is so constructed as to integrally rotate along with rotating shaft 16. On the outer circumferential surface of rotor 30, at least one roller 34 is arranged so as to rotate about its own axes. A tube 36 which is filled with blood or other fluid material is placed between rotor 30 and stator 26. Tube 36 is clamped between respective rollers 34, which are attached to rotor 30, and inner circumferential surface 28a of stator 26, thereby maintaining tube 36 in a closed state at the point at which it is clamped.
Thus, in a conventional roller pump 10, rotor 30 is rotated by the rotational motion of rotating shaft 16 driven by drive mechanism 14, and the clamped portions of tube 36 move according to the revolution of rollers 34 around rotating shaft 16. Therefore, fluid inside tube 36 is transferred according to the revolution of rollers 34. The rate of rotation of the rotating shaft 16 and hence the rollers 34 is normally adjustable so that the pumping rate of the fluid within tube 36 can be adjusted. However, the pumping rate can also be adjusted by adjusting the degree to which the rollers compress the flexible tube. This can be done in peristaltic pump assemblies by providing an adjustment mechanism for adjusting the distance between the axes of the rollers and hence the distance between the roller surface and the inner circumferential surface 28a of stator 26. Another important reason for peristaltic pumps to be adjustable in this fashion is that the compressibility, size, and other qualities of the flexible tube can vary considerably.
A rotor assembly 30xe2x80x2 having an adjustable occlusion capability, as shown in FIG. 2, comprises a rotor hub 40, and opposing roller slides 42, each of which carries at least one roller 34 on the outer circumferential surface thereof. The roller slides 42 are extended or retracted from the hub 40 by turning the knob 44 on the top of the rotor hub. The extension or retraction of the roller slides thereby changes the occlusion of the flexible tube within the peristaltic pump. The roller slides 42 should be held securely to avoid knocking of the slides on the side, top, or bottom surfaces of the slot in the hub 40, particularly as the rollers 34 roll onto or off of the flexible tube in the pump. Because the flexible tube in a peristaltic pump is typically located in an approximately 180xc2x0 arc around the rotating rotor, each roller 34 rolls onto and then off of the flexible tube once during each revolution of the rotor. Any knocking of the roller slides against the walls of the rotor hub produces a noise which has been found unacceptable in a surgical environment.
The roller slides in a peristaltic roller pump must therefore be held securely in order to avoid the unacceptable noise of the roller slide knocking against the hub. In order to prevent this knocking noise, the gap between the roller slide and the hub surface must be within approximately 0.001 inch on both the sides and the top and bottom of the slide. It is difficult and expensive to fabricate the hub and roller slides to maintain the gaps within this specification. The roller slides and hub are typically fabricated of aluminum and are anodized after machining. Considering the variation in geometry introduced by the anodization process, the height and width of the roller slides and hub must be machined to tolerances of approximately +/xe2x88x920.0001 inch in order to obtain a 0.001 inch or less gap between the roller slides and hub. It is not practical to machine the parts to these tolerances. For the various occlusion mechanisms on the market, the most common approach used to obtain the 0.001 inch or less gap between the roller slides and hub relies on part size classification and custom fitting of parts. As a result, the roller slides in one pump do not necessarily fit properly in the hub of another pump, and hence classification and custom fitting of parts does not allow for easy service or replacement of the roller slides.
Accordingly, there is a need in the art for an improved system for mounting the roller slides in the hub of a rotor assembly which substantially eliminates the potential for knocking noises and significantly relaxes the machining tolerances for the roller slides and hub.
The present invention overcomes the disadvantages of the prior art by providing an adjustable bushing for use in a roller pump. The adjustable bushing comprises a preferably wedge shaped bushing member and a spring. The spring biases the wedge shaped bushing member in a recess in a portion of the roller pump; thereby compensating for any gap or spacing between the roller slide and the hub.
More particularly, the present invention is directed to a roller pump comprising a stator, a rotor assembly including a rotor hub, a first roller slide and a second roller slide slidingly disposed within the rotor hub, and each of the roller slides supporting a roller. At least one adjustable bushing is mounted within at least one of the roller slides to compensate for any gap or spacing between the roller slide and the hub. In a preferred embodiment, at least one of the roller slides includes a recess and the at least one adjustable bushing is at least partially disposed within the recess. The at least one adjustable bushing preferably comprises a bushing member and a spring member, the spring member biasing the bushing member within the recess. More preferably, the bushing member has a wedge shaped configuration and the recess is correspondingly tapered within a surface of one of the roller slides.
In a preferred embodiment of the present invention, the at least one adjustable bushing comprises a first adjustable bushing disposed within a side surface of at least one roller slide and a second adjustable bushing disposed within one of a top and a bottom surface of at least one roller slide.
The present invention is also directed to a rotor assembly for a peristaltic pump comprising a rotor hub, at least one roller slide slidingly disposed within the rotor hub, a roller supported by the at least one roller slide, and at least one adjustable bushing mounted within the at least one roller slide. The at least one roller slide preferably includes a recess and the at least one adjustable bushing is at least partially disposed within the recess. More preferably, the at least one adjustable bushing comprises a bushing member and a spring member, the spring member biasing the bushing member within the recess